Here are some ideas for you tomorrow:
1. Listen to some of his masterpieces.
2. Practice his organ or keyboard works.
3. Compose a short piece influenced by Bach's style or technique.
4. Sing a chorale (any part) harmonized by Bach. In fact, you can sing any part of his organ piece that you are practicing, too.
5. Read an article or a part of the book on Bach.
6. Watch a video or two with Bach's music.
7. Write an article about Bach and his art and share it with some of your friends.
8. Improvise a piece in the Bach's style.
9. Sight-read a few of Bach's organ pieces.
10. If you have a church service - perform one or more of Bach's chorale preludes or other pieces (you can do the same this Sunday, too).
[UPDATE: and of course, eat some cake in his honor.]
While the above things can be done by you alone, there is some magic in doing things TOGETHER. I have an idea:
By Sunday evening write 2-3 sentences about why do you like Bach and his art. With your permission, I will share all I receive from my readers (with names and their countries) in a special article after this weekend.
[UPDATE: you will find the answers here.]
By the way, this Saturday, I'll be playing an all Bach recital at Vilnius University St. John's church. Here is it's video preview (it's in Lithuanian but I think you will get it pretty easily). The opening picture has the above quote by Helmut Walcha.